A secondary battery having good application to various product groups and good electric characteristics such as high energy density is widely applied to not only portable devices but also an electric vehicle (EV) or a hybrid electric vehicle (HEV) driven by an electric driving source. The secondary battery has a primary advantage of greatly reducing the use of fossil fuels and a secondary advantage of generating no byproduct in use of energy, and thus attracts attention as a new energy source for enhancing environment-friendly and energy-efficient properties.
Lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries or the like are widely used as secondary batteries at the present. Such a unit secondary battery cell has an operating voltage of about 2.5V to 4.2V. Therefore, if a higher output voltage is demanded, a plurality of secondary battery cells may be connected in series to configure a battery pack. In addition, according to a charge/discharge capacity demanded to the battery pack, a plurality of secondary battery cells may also be connected in parallel to configure a battery pack. Therefore, the number of secondary battery cells included in the battery pack may be various set depending on a demanded output voltage or charge/discharge capacity.
Meanwhile, if a plurality of secondary battery cells is connected in series or in parallel to configure a battery pack, in general cases, two or more secondary battery cells are assembled to configure a battery module, a plurality of battery modules is assembled to configure a battery module assembly, and other components are added to the battery module assembly, thereby configuring a battery pack. At this time, the shape of the battery module assembly is determined depending on electric connection or mechanical connection among the plurality of battery modules.
FIG. 1 shows an example of an existing battery module assembly.
The battery module assembly 1 depicted in FIG. 1 is disclosed in Korean Unexamined Patent Publication No. 10-2013-0017289, and this document discloses that a coupling force is obtained using a bolt 2 in order to obtain a mechanical connection between battery modules 3. However, if the battery modules 3 are coupled using the bolt 2, a hole should be separately formed in a battery module frame for the bolt coupling. In addition, when battery modules are coupled using the bolt 2, a sufficient space capable of supporting the bolt 2 is required around the hole for the bolt coupling in order to give mechanical strength. Therefore, the above technique, in which a hole is directly formed in the battery module frame and the bolt 2 is coupled to the hole, has disadvantage in terms of space utilization.